There are many devices that use the energy of the sun to provide a useful benefit. As an example, solar cells are often used to convert the energy of the sun into electricity. These devices are often used in remote locations to power pumps, lights, telecommunication devices and the like and must be extremely robust and reliable. There are also other devices that require the energy of the sun, for successful operation, such as water heating devices. The effectiveness of these devices is generally improved if the device can track the movement of the sun to enable the device to absorb as much as possible of the sun's energy. Therefore, it is well known to provide some form of solar tracking apparatus.
A common type of apparatus uses one or more photoelectric cells which are operatively associated with some form of electric drive motor. There are several disadvantages with this type of apparatus including the fragile nature of the photoelectric cells, and the need to have a source of electric power, such as battery power, or electricity generated from the solar cells. This type of apparatus requires a relatively high degree of servicing, maintenance, and repair, and therefore does not find particular use in remote locations.
An attempt has been made to do away with the need for electric motors and photoelectric cells. For instance, international patent application WO 92/11496 describes an apparatus which has two cylinders. Each cylinder is filled with a low boiling liquid (which can include ether). Around each cylinder is a parabolic reflector. One cylinder and its parabolic reflector faces the east and the other cylinder and its parabolic reflector faces the west. As the sun rises in the east, the sun's rays will be concentrated by the parabolic reflector onto the east facing cylinder to boil the liquid in the cylinder to create a gas which causes the cylinder ram to extend and this causes rotation of a framework on which solar cells are attached. An advantage with this apparatus is that photoelectric cells and electric motors are not required. However one main disadvantage is that the parabolic reflectors are relatively high maintenance and the reflector (or the transparent glass or plastic cover) must be kept very clean. Also, significant heat is required to boil the liquid into the gas which means that the apparatus may not work immediately. Moreover, working with gas requires particular design principles and the overall effect is that this type of apparatus is not entirely reliable and robust.
A further disadvantage with many existing solar tracking devices is that the device does not return back to the “east facing” position during the night and only does so at the beginning of the next day. This makes this type of device less efficient.
A further disadvantage with many existing solar tracking devices is that the devices are not particularly stable or effective under high wind conditions
Therefore, there would be an advantage if it were possible to develop a solar tracking apparatus that did not require photoelectric cells that did not require an electric motor to track the apparatus, that did not require parabolic reflectors, and that did not require boiling a liquid into a gas to provide the working force for a cylinder.
It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.